An antenna arrangement of this kind is known from EP 1 588 454 B1. This anticipatory document describes the use of, for example, an antenna arrangement, which can be vertically oriented, having a reflector. On the vertical lateral limiting lines of the reflectors two lateral webs are formed transversely, and in particular perpendicularly, to the reflector plane so as to protrude in the direction of radiation. The dual-polarized radiators arranged one above the other in the vertical direction sit between these lateral webs. According to this anticipatory document also, the base of the supporting mechanism and/or balancing means of the associated radiator assembly is capacitively connected (i.e. without electrical-galvanic contact) to the reflector or coupled thereto by connecting a cap in series. For this purpose, the reflector has a recess in which the non-conductive cap engages and is secured and in turn holds the supporting mechanism and/or balancing means or the base of the supporting mechanism and/or balancing means of the dual-polarized radiator. The internal conductor can be installed as is described in the above-mentioned prior art in this case. A flat antenna is known from DE 697 25 874 T2. It comprises a ground plane layer that is capacitively coupled to a base unit. A dielectric layer is provided between these two layers.
Antenna arrangements, in particular for a mobile radio base station, are also known for example from WO 00/039894 A1. This anticipatory document describes a reflector that can be vertical oriented. On the two vertical and mutually parallel outer, laterally located limits of the reflector, a lateral web is formed that protrudes in the direction of radiation and therefore transversely to the reflector plane. A plurality of dipolar arrangements consist of what are known as vector dipoles. They are provided radiating in two mutually perpendicularly oriented polarization planes one above the other in the vertical direction. In terms of construction, these vector dipoles are similar to dipole squares. Nevertheless, feeding takes place in such a way that despite the horizontally or vertically oriented dipoles, overall the dipole arrangement acts as an X-polarized antenna in which the two polarization planes that are perpendicular to each other are oriented at an angle of +45° or −45° with respect to the vertical or horizontal.
It can be gathered from WO 2005/060049 A1 that the dual-polarized radiators, which sit upstream of a reflector, may be provided with a capacitive outer conductor coupling. Axial holes that run perpendicular to the reflector plane are therefore introduced in each half of the two supporting mechanisms and/or balancing means that are rotated by 90° with respect to each other. Rod-shaped coupling elements 21 that are galvanically connected to the reflector project into these holes and are surrounded by cylindrical insulators onto which the pairs of supporting halves of the dual-polarized radiator assembly that are arranged rotated by 90° with respect to each other can be placed with the total of four axial holes. An internal conductor for feeding the two mutually perpendicular polarizations of the radiator assembly can be laid inside two rod-shaped coupling elements from the back of the reflector in each case.
Finally, antenna arrangements with reflectors are known on the longitudinal lateral regions of which, i.e. on the longitudinal or vertical lateral surfaces of which, longitudinal webs that protrude forwards from the reflector plane are provided, as may be gathered for example from the anticipatory documents WO 99/62138 A1, U.S. Pat. No. 5,710,569 A or EP 0 916 169 B1.
An alternative embodiment according to this anticipatory document discloses that instead of an electrically conductive reflector, conventionally in the form of a metal sheet, a printed circuit board may also be used on which the reflector is constructed. In this case, the electrically conductive ground plane is preferably omitted on one side of the printed circuit board or the cap is also provided with insulation in this region.
Finally, reference is made to WO 01/41256 A1 which describes a patch antenna. This patch antenna is arranged on a dielectric printed circuit board, which is provided with an electrically conductive layer on both sides. On the conductive dimension in the beam direction, a cross-shaped recess is provided, above which a radiator patch is arranged.
By contrast, the illustrative technology herein creates an improved dipolar shaped antenna arrangement which includes beam shaping possibilities and still has a simple construction.
The invention creates an improved antenna arrangement that can be easily and highly accurately produced with exactly predetermined radiation properties while avoiding potential sources of disruption such as undesirable intermodulations.
It has previously been conventional in the prior art to usually use reflectors made from a metal sheet. The radiator modules have been constructed on the reflectors. The longitudinal lateral limits have been in the form of longitudinal webs. These webs protrude transversely to the reflector plane. The webs can be constructed at a suitable location based on arranging the radiators between the reflector plane lateral external limit and the centrally arranged radiators. These longitudinal webs could be adjusted for example between a perpendicular orientation with respect to the reflector plane through to an angular orientation in such a way that desired beam shaping was possible.
If, by contrast, one wanted to use reflectors in the form of printed circuit boards (what are referred to as PCBs) which were provided on one side with an electrically conductive ground plane, then this required the webs needed for beam shaping to be connected to the ground plane of the printed circuit board by means of screw connections or soldered joints in order to achieve a definite galvanic connection at that point. In addition to being laborious, this assembly work caused potential intermodulation sources or disruption.
By contrast it is now proposed, starting from a printed circuit board which is preferably provided on its radiator side with an electrically conductive ground plane and a insulating layer located above it, to place a reflector frame thereon. The reflector plane is provided with a coupling surface parallel to the ground plane of the printed circuit board. The desired longitudinal and/or transverse webs that are required for diagram shaping in turn are constructed on this coupling surface. In other words, a capacitive reflector frame coupling is proposed, for a dipolar shaped radiator assembly (preferably a dual-polarized radiator assembly), that allows the longitudinal and/or transverse webs required for diagram shaping to be capacitively coupled to a ground plane sitting on a printed circuit board.
In a preferred embodiment, the reflector frame provided according to the invention can be made from an electrically conductive metal, for example aluminum. In particular, a reflector frame of this kind can be produced by way of all suitable production processes, for example by a casting process, by shaping, milling, etc. It is also possible to produce a reflector frame of this kind from an electrically non-conductive material, for example plastics material, which is coated with an electrically conductive layer.
In a particularly preferred embodiment, the reflector frame is produced from a punching, in particular from a metal sheet, by means of a punching/bending process. In the process it is possible by way of suitable punching and subsequent canting to produce an appropriate three-dimensionally shaped reflector frame from a metal sheet in which the lateral limits or webs are assembled from the metal sheet plane by canting and orientation transverse to the reflector plane. At the same time, mutually offset transverse webs can be provided in the add-on direction, whereby the individual radiators or radiator groups are delimited from each other. These transverse webs can also be assembled transversely, and in particular perpendicularly, to the reflector plane by punching and canting or bending.
In a particularly preferred embodiment tongues are formed on the outside of the thus formed transverse webs so as to project away from each other in the axial extension. The tongues can engage in corresponding slotted recesses in the longitudinal lateral limitations if the longitudinal lateral limit has also been assembled in corresponding transverse orientation to the reflector plane following the punching and canting process.
Capacitive coupling of the reflector frame on a printed circuit board without galvanic connection between reflector and printed circuit board ground plane is therefore provided. A stable intermodulation-free connection is provided. A clearly defined spacing and/or a clearly definable size of the coupling surfaces means that an exactly defined coupling between ground plane of the printed circuit board and the reflector frame may also primarily be ensured.
Finally quick and uncomplicated assembly is also possible, whereby sources of error are reduced and above all soldered joints are omitted on the reflector.
The completely assembled unit, comprising reflector frame and printed circuit board, forms a self-supporting unit. The reflector frame can be connected to the printed circuit board using any suitable means, for example by means of clips, a double-sided adhesive tape, separate adhesives, etc.
The ground plane on the printed circuit board is preferably originally provided with an insulating layer, for example in the form of paint, in particular a solder resist, a film or some other plastics material layer, which allows metallic isolation from the reflector frame. If the reflector frame is glued by means of a double-sided adhesive tape then this already provides an insulation and therewith metallic isolation between the electrically conductive reflector frame on the one hand and the ground frame on the printed circuit board on the other, so a separate insulating layer can even be omitted on the ground plane.